More than 180 of the world's largest investors, with collective assets of $13tn, put their combined weight behind a passionate call for strong US and international action on global warming in New York today.

"We cannot drag our feet on the issue of global climate change," said Thomas DiNapoli, who heads the $116.5bn New York state pension fund. "I am deeply concerned about the investor risks climate change presents, and the human cost of inaction is unthinkable."

The summit drew together managers of the world's leading investment funds, including those from HSBC, Henderson, Schroders, Société Générale and Scottish Widows, and pensions funds from California public employees to the BBC and Church of England. It was aimed at overcoming entrenched opposition within the US and elsewhere to climate change legislation, by showcasing the scale of investor support for climate change action and the potential for mobilisation of private capital.

"For anybody who suggests that regulating carbon or acting on climate change is impractical, here is appropriate contradiction," said Mindy Lubber, the president of Ceres, the green investor network that helped organise the conference. However, she warned: "Investors are ready to put money into green tech, but they are not going to act until the government acts and makes clear that the right incentives are in the right place."

The investors' endorsement for action on climate change comes amid signs of a loss of momentum in the final stretch of negotiations towards a deal to tackle global warming in Copenhagen in December. The group warned that failure to act effectively would have disastrous consequences in human and economic terms.

In contrast to inaction, Lord Nicholas Stern, author of the 2006 Stern report on the economics of climate change, said: "Building a low carbon economy creates opportunities for investment in new technologies that promise to transform our society in the same way as ... electricity or railways did in the past." He added: "Unmitigated climate change poses a threat to the global economy."

In their joint statement the investors supported the tougher targets for reducing greenhouse gas emissions put forward for negotiation at Copenhagen, including cuts in greenhouse gas emissions by developed countries of 25-40% by 2020.The conference was held amid rising frustration that the US Congress and the international negotiations are faltering in the final days before Copenhagen. Stern, in his remarks, said it was time to move away from the "quarrelsome stupid politics" surrounding climate change.